The use of tread wear indicators is not new and the use of tread wear indicators is mandated by law in many countries. A variety of such indicators are known. Once such type employs colored indicia below the tread for a visual indicator of wear. Other types use tie-bar type elements in the tread grooves.
The practical problem with the colored indicators of the type mentioned is that there is no way for the operator to determine the level of wear until the tire is worn. When the tire employs the tie-bar type wear indicator, it can be difficult to determine the level of wear.
U.S. Pat. No. 6,523,586 discloses wear indicators for a tire tread wherein, in a series, or predetermined closely located grouping, of related marks, the marks disappear as the tire is worn. While this provides continuous information to the consumer, the complexity of forming the tire is increased due to the need to form multiple different marks that appear only after a defined amount of wear.
A tread wear indicator which is readily integrated into a tire and which reliably measures tread wear in a manner easily monitored by a vehicle operator is, accordingly, desired. Additionally, a tread wear indicator is desired that operably is convenient for the end user (i.e. can be read from within the vehicle when raining, at night (darkness), etc.) and can predict tire life based on the exploitation history of the tire.